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  1. KrisBlueNZ

    Rewiring 7-band EQ

    Yes, that's right. It's called a buffer because it doesn't provide any voltage gain; if it had voltage gain it would be an amplifier, or an attenuator if the gain was less than 1. It provides current gain, or impedance reduction. It has a high-impedance input that can be driven properly by a...
  2. KrisBlueNZ

    7 Transistors Triangle Wave Generator (650Khz)

    Q4's collector voltage isn't constant, so I guess its function isn't simply static - its Miller capacitance at least will be relevant. I tried changing Q3 and Q4 to 2N2369s in the simulation and the emitter node waveform squares up slightly, but you're probably right that it's not worth worrying...
  3. KrisBlueNZ

    7 Transistors Triangle Wave Generator (650Khz)

    Isn't it also important to use high-frequency transistors for Q1~4?
  4. KrisBlueNZ

    7 Transistors Triangle Wave Generator (650Khz)

    Nice! Thanks for the explanation. I can follow it but I don't think I have a complete and natural understanding of it yet. I simulated it, and got good results. This will allow me to explore it further, if I have the time and inclination to :-) Would it be better to use a transistor array for...
  5. KrisBlueNZ

    Rewiring 7-band EQ

    That's great! That's an impressive result for a first project. The buffer circuit consists of two inverting stages. Each stage has a gain of -1, which means the output amplitude is the same as the input amplitude but the signal is inverted. I'll describe the left channel; the right channel is...
  6. KrisBlueNZ

    7 Transistors Triangle Wave Generator (650Khz)

    That looks like a nifty little circuit! How will you get the thermal tracking for the current mirror transistors if you use discrete components? Would you consider tidying up the schematic by adding wires so the components don't touch so closely? I would like to see a circuit description, yes.
  7. KrisBlueNZ

    Connect to Home Phone Wirelessly

    In my previous post I said that the BMW key-fob cellphone can be programmed so that long-pressing a number button dials a preconfigured phone number. I don't actually know whether that's true; I should have said that that cellphone MAY be able to be programmed to do that.
  8. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    Yes, this seems pretty clear from Figure 6-1 in the data sheet. When PSA is set to 1 (i.e. the prescaler is being used as a postscaler for the watchdog timer), the selector to the left of the "SYNC 2 Cycles" block selects the output of the T0CS selector directly. When PSA is 0, this signal...
  9. KrisBlueNZ

    FET switching for 24V

    You could use a 12V zener from the switch MOSFET's gate to the positive supply rail (i.e across R2) if you also add a resistor between the driver's drain and the switch's gate. You could also just break the connection from the driver drain to the switch gate and insert a 12V zener with its...
  10. KrisBlueNZ

    reverse engineering help

    If it all went bang when you connected your oscilloscope's ground lead to the ground rail of the circuit, your mains supply is probably reversed, and ideally this should be fixed. You should have continuity from the GND rail of the board to the Neutral pin of the mains plug. If you have...
  11. KrisBlueNZ

    Circuits with 15 to 25 components.

    https://www.google.com/search?q=sound+generator+circuit+schematic&tbm=isch
  12. KrisBlueNZ

    moc3043 and tlp3043

    What is the purpose of the testing? Are you planning to re-sell the units that pass? Or are you simply looking for a go/no-go test? Also, how much (if any) manual intervention can you provide on a per-unit basis? The MOC304x has some circuitry inside it - the zero-crossing detector - that can...
  13. KrisBlueNZ

    Hitachi LED TV won't turn on

    Looks like a Sanken STR-A6069H http://www.digikey.com/product-detail/en/STR-A6069H/STR-A6069H-ND/3661844 Ex stock, USD 2.29 Good luck!
  14. KrisBlueNZ

    TDA2030A Headphone Amp Gain too high

    Of course! The kind of value that's useful in audio applications is not difficult to manufacture on silicon; it's impossible! That is (I assumed) the reason that the base connections were both brought out to pins on the LH0002 - for connection of an external capacitor! Yes, and for very good...
  15. KrisBlueNZ

    TDA2030A Headphone Amp Gain too high

    Is that AN227 "Applications of Wide-band Buffer Amplifiers"? I just had a quick look at that one. It doesn't help me much. Yes, I read that one already. It doesn't show the capacitor between the bases of the output transistors! Nor does AN227. That's disappointing, because that capacitor is...
  16. KrisBlueNZ

    Volumetric Visualizer display Feedback wanted

    Cool project! You are very resourceful.
  17. KrisBlueNZ

    Time Delay Relay Help!

    I don't understand your second paragraph. With the design I'm suggesting, the mirrors WILL unfold on ACC. When ACC goes ON, they unfold, and when ACC goes OFF, they fold up. The only problem is during cranking, when ACC disappears; my suggestion was to disable the +12V during cranking, using a...
  18. KrisBlueNZ

    Time Delay Relay Help!

    When you say that it "drops" ACC and IGN, do they go to zero volts? In older, simpler cars, ACC and IGN remain energised, but the voltage on them dips because of the heavy load on the battery due to the starter motor. But I guess you have a car that deliberately drops ACC and IGN to zero...
  19. KrisBlueNZ

    Time Delay Relay Help!

    When the mirror is fully extended or retracted, if the current drops to 1 mA and the motor stops, there are limit switches, not just stops, and I recommend the arrangement I just described. It's equivalent to what you described using a changeover relay to switch +12V between 85 on the unfold...
  20. KrisBlueNZ

    Time Delay Relay Help!

    Hi stoggy and welcome to Electronics Point :-) Thanks for the thorough and clear description. Do the mirrors need the voltage to be applied for a limited amount of time? Or do they have limit switches so that when the mirror reaches the end of its travel, the motor stops automatically? If the...
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